Semiconductor wafer (“wafer”) fabrication often includes exposing a wafer to a plasma to allow the reactive constituents of the plasma to modify the surface of the wafer, e.g., removal material from unprotected areas of the wafer surface. The resulting wafer characteristics following the plasma fabrication process are dependent on the process conditions, including the plasma characteristics and wafer temperature. For example, in some plasma processes a critical dimension, i.e., feature width, on the wafer surface can vary by about one nanometer per degree Celsius of wafer temperature. It should be appreciated that differences in wafer temperature between otherwise identical wafer fabrication processes will result in different wafer surface characteristics. Thus, a drift in process results between different wafers can be caused by variations in wafer temperature during plasma processing.
A general objective in wafer fabrication is to fabricate each wafer of a given type in as identical a manner as possible. To meet this wafer-to-wafer uniformity objective, it is necessary to control fabrication parameters that influence the resulting wafer characteristics. Therefore, it is necessary to control the wafer temperature during the plasma fabrication process. Current plasma processing devices for wafer fabrication do not include effective wafer temperature control capabilities. Therefore, a need exists for accurate control of wafer temperature during a plasma fabrication process.